The present invention relates to an ignition coil for ignition systems in combustion engines.
More particularly, it relates to an ignition coil with at least one secondary connection part.
Ignition coils having a sleeve-shaped secondary connection part which projects out of the housing of the ignition coil and conducts high voltage to the spark plug are known in general. These secondary connection parts have a connection dome and a spark plug terminal which is permanently coupled with the latter.
The location where the connection dome is coupled with the spark plug terminal is constructed in such a way that the spark plug terminal can be swiveled to a slight extent relative to the connection dome which rigidly projects from the housing of the ignition coil. This swiveling serves to compensate tolerances between the ignition coil which is fastened directly to the cylinder head and the spark plug which is fixed in a spark plug recess of the cylinder head of the internal combustion engine.
Since the spark plug recess, for purposes of mounting, has a greater inner diameter than the outer diameter of the spark plug or spark plug terminals connected with the ignition coil, it may happen in rare instances when mounting the ignition coil on the cylinder head that the spark plug terminal does not slide onto the spark plug, but instead enters the intermediate space between the wall of the spark plug recess and the spark plug. This faulty mounting is generally not detected during the initial operation of the internal combustion engine because, with the high voltage provided by the ignition coil, the improperly contacted spark plug receives a sufficient, though reduced, ignition voltage by sparkover or arcing.
However, the voltage which is transmitted in this way is not sufficient for generating an ignition spark at the defectively contacted spark plug under adverse operating conditions caused by weather and aging. This leads to misfiring and to emission of unburned fuel from the internal combustion engine, which must be prevented.